Microbiological Environment Research Articles

From `ecopathology' to `agroecosystem health'

The `epidemiologic revolution' of the 1960s arose in response to the inability of reductionist methods to provide practical solutions to the complex problems of health and production in livestock systems. In a farm, there are not only interactions between animal factors and herd husbandry factors such as feeding, housing, and microbiological environment, but also with a number of other `non-animal' factors. For this reason, a `global' or `holistic' approach, aimed at explaining animal health status within the overall dynamic of a livestock production system, was developed in France under the title of `ecopathology'. In ecopathology, the discipline of epidemiology is integrated into a systemic approach, including: the development of a preliminary conceptual model, sampling based on the structure of the livestock production system, the establishment of a field study by a multidisciplinary team, the organization and management of the animal health and production information, data analysis, the distribution of results to all participants and the development of a preventive medicine programme. The farm is also influenced by the social, economic and environmental setting to which it belongs. To account for this, a change of scale is necessary. The three elements of the livestock production system considered in ecopathology (farmer, herd and resources), at the level of the agroecosystem become a human community (farmers, consumers, decision-makers), an animal population, and the complex of human, social and economic conditions within the system. The concept of agroecosystem health is closely linked to the overall principle of improving the sustainability of the system. This and other measures of the health status of an agroecosystem can be assessed with methods developed by epidemiologists and other disciplines within a system's perspective. In this systems view, ecopathology provides a basis for assessing herd health whereas agroecosystem health develops the broader context into which ecopathology contributes.

The Growing Problem of Nosocomial Bacterial Resistance

Today’s nosocomial microbiological environment is characterised by increasing numbers of drug-resistant bacteria, notably methicillin-resistant staphylococci, glycopeptide-resistant enterococci, extended-spectrum β-lactamase-producing Enterobacteriaceae and hyperproducers (or stably derepressed mutants) of AmpC β-lactamases. Although the precise prevalence of these pathogens varies between institutions and between countries, they are now sufficiently widespread to pose a major clinical and therapeutic problem.

Incidence of biopsy-proven primary glomerulonephritis in an Italian Province

Between January 1, 1970, and December 31, 1994, 1,926 cases of biopsy-proven primary glomerulonephritis (PGN) were diagnosed in an adult population (>15 years of age) in a northwestern region of Italy with approximately 3.5 million inhabitants. The principal long-term changes were an increase in the absolute number of biopsies per year, an increase in the mean age of patients undergoing biopsy (from 29.3 ± 12.2 years to 47.0 ± 17.8 years), an increase in the percentage of patients older than 65 years (from 1.7% to 20.4%), and an increase in the percentage of isolated urinary abnormalities as an indication for biopsy (from 3.5% to 29.6%). In the total biopsy material, immunoglobulin A glomerulonephritis (IgA-GN) is the most frequent type (26%), followed by membranous glomerulonephritis (MGN; 20%). An incidence study was begun in 1990; this survey was restricted to the population of the province of Torino (approximately 2 million inhabitants) as only this area completely refers to the nephrologic centers that entered patients into this study. The overall incidence of PGN is 4.68 new cases/yr/10 5 population with a predominance of males (>2:1); IgA-GN is the most common type (1.47/yr/10 5 population [34.5%]) in the overall population. In the elderly, cases of PGN are twice as high as in adults (8.19/yr/10 5 population v 4.02/yr/10 5 population in the 65 to 74 year and 45 to 54 year age groups, respectively); MGN mainly accounts for this high incidence (3.4/yr/10 5population), while the nephrotic syndrome is the most common indication for biopsy (53.8%). A comparison with the incidence in the same area in the early 1970s is evaluable only for PGN, which was mainly registered in the age groups for which an unrestricted biopsy policy was already in place (15 to 35 years). In contrast with a misleading increase of all types of PGN, which is in reality due to the extension of the biopsy policy to older and asymptomatic patients, membranoproliferative glomerulonephritis type I shows a countercurrent decrease from 0.43 to 0.13/yr/10 5 population. Evidence of a simultaneous decrease in severe cardiac valvulopathy, due to rheumatic fever, is also provided. We feel that before epidemiologic conclusions can be reached, a clear understanding of one's own biopsy policy is essential. An apparent change in the PGN rate in our region over the last 25 years mainly depends on modifications in our biopsy policy, most probably coupled with a change in the threshold of detection of symptoms in the general population. At present, according to our experience, IgA-GN is the most common type of PGN in the total bioptic material, as demonstrated in other European countries, while the elderly show a peculiar pattern with a higher PGN incidence, mainly represented by MGN and heralded by the nephrotic syndrome. We also confirm that membranoproliferative glomerulonephritis type I is indeed decreasing in parallel with changes in the microbiologic environment.

An overview of microbiologically influenced corrosion of metals and alloys used in the storage of nuclear wastes

Microbiologically influenced corrosion has been documented for all metals and alloys currently in use or proposed for packaging nuclear wastes, with the possible exception of titanium. Selection of a material that will provide a reliable physical barrier to prevent leakage of radionuclides for 103–106 years will depend on a thorough understanding of mechanisms for microbiologically influenced corrosion; the geological, microbiological, and chemical environments of storage sites; and their evolution over time.Key words: nuclear waste storage, microbiologically influenced corrosion, biofilms.

Emerging Infectious Disease

INFECTIOUS DISEASES have always played a major role in defining our daily lives. Empires have risen and fallen from events related to contagious diseases. Human and animal populations have been devastated—and controlled—by the outbreak of epidemic infectious diseases. The last century and a half has brought great understanding of the biology of microbial agents affecting man and his environment. With this knowledge, we have had periods of extreme optimism regarding man's ability to control and even conquer the pestilences affecting our health. However, this euphoria about man's ability to positively influence our interaction with our microbiological environment is often followed by periods where we doubt the long-term effect of our interactions. During the last century, we have seen a marked reduction in the prevalence of many infectious diseases that used to carry a high morbidity and mortality. Severe disease related to infection with group A streptococci such as erysipelas, rheumatic

A prospective study of the microbiological environment of the genitourinary tract in Hong Kong Chinese women during pregnancy.

Microbiological colonization of the genitourinary tract in pregnancy is associated with an increased risk of preterm labour and delivery. In our population, the risk of preterm labour is relatively low, and the purpose of this study was to examine the microbiological environment of the genitourinary tract to determine whether it differed from that reported in populations where the rate of preterm delivery is higher. A prospective study was made in 367 unselected women between 16 and 24 weeks' gestation. Although the rate of colonization with Candida species was higher than in most other studies (30.2%), colonization with Gardnerella, Group B Streptococcus, Trichomonas and Chlamydia was uncommon (1.9%, 0.8%, 0.6% and 3.5% respectively). Significant bacteriuria was also uncommon, occurring in only 4.9% of cases. The results of this study confirmed a relatively low incidence of colonization of the genitourinary tract in this population of women with a low incidence of preterm delivery. These findings suggest that low levels of colonization may be related to a low incidence of preterm delivery in our patients.

La surveillance sanitaire des échanges d'embryons bovins issus de fécondation in vitro

The production of embryos fertilised in vitro is part of the third generation of biotechnologies applied to reproduction and is now undergoing development and application in the field. International exchanges of these embryos have already commenced. However, there are certain associated health risks. In decreasing order of importance, these involve dangers inherent in the initial biological material from which gametes and various somatic cells vital to such production (follicular and tubal cells, etc.) are derived, then possible external contamination during the production process, and finally storage and transport. Although the research which has been conducted on the interaction between these embryos and pathogens is still rather limited, as the technique has been under development for only a short time, it is clear that the media in which the oocytes undergo maturation, the spermatozoa undergo capacitation or the embryos are cultured constitute excellent indicators of the potential microbiological or viral environment. This can be utilised in health surveillance of the manipulations. Recently, specific recommendations for making such exchanges safe have been inserted into the Office International des Epizooties International Animal Health Code. These recommendations are based on the concept of official approval of specific embryo transfer teams and examination of animals from which gametes are obtained.

Specificity of a protective memory immune response against Mycobacterium tuberculosis

We have investigated the memory T-cell immune response to Mycobacterium tuberculosis infection. C57BL/6J mice infected with M. tuberculosis were found to generate long-lived memory immunity which provided a heightened state of acquired resistance to a secondary infection. The T-cell response of memory immune mice was directed to all parts of the bacilli, i.e., both secreted and somatic proteins. Major parts of the memory T-cell repertoire were maintained in a highly responsive state by cross-reactive restimulation with antigens present in the normal microbiological environment of the animals. A resting non-cross-reactive part of the memory repertoire was restimulated early during a secondary infection to expand and produce large amounts of gamma interferon. The molecular target of these T cells was identified as a secreted mycobacterial protein with a molecular mass of 3 to 9 kDa.

A comparison of the seroepidemiology of chlamydial infection in pigeon fanciers and farmers in the U.K.

A detailed comparative seroepidemiological study of antibody responses was performed in 271 pigeon fanciers and 100 farmers. Overall 73% of pigeon fanciers had IgG antibodies at a titre greater than or equal to 16 to Chlamydia pneumoniae, 39% to Chlamydia psittaci, and 6.6% to Chlamydia trachomatis. The prevalence of chlamydial antibodies was significantly lower in the farmers at 47% for C. pneumoniae, 6% for C. psittaci, and 2% for C. trachomatis. Both populations were exposed to complex microbiological and antigenic environments: 50.5% of the pigeon fanciers had antibodies to pigeon antigens, 34% to egg membrane, and 0.73% to yolk sac antigen, and 59% of the farmers had antibodies to Micropolyspora faeni, but the high prevalence of chlamydial antibodies could not be attributed to interaction with these antigens. There was considerable overlap of chlamydial antibody responses in the pigeon fanciers but not in the farmers: 36% of the pigeon fanciers had antibodies to C. pneumoniae alone, 5% to C. psittaci alone, and 31% to both agents, whereas only 3% of farmers had antibodies to both C. pneumoniae and C. psittaci. The high prevalence of antibodies to C. psittaci in the pigeon fanciers is compatible with the known avian reservoir for this infection. The particularly high prevalence of antibodies to C. pneumoniae suggests that complex interactions may be occurring in a population exposed to two chlamydial organisms, whereby infection with one species may provoke an anamnestic response against other chlamydial organisms with which the subject has previously been infected.

Endotoxic activity in faeces of mice from different microbiological environments

Chromogenic Limulus amoebocyte lysate (LAL) tests were evaluated for measuring endotoxic activity in faeces of mice from different microbiological environments. Faeces of BALB/c mice from germ-free (GF), specific-pathogen-free (SPF) and conventional (CV) colonies had no inhibitory activity on the test reaction. GF and SPF faeces had heat-labile non-specific amidase activity which gave false-positive reaction, while CV did not. GF faeces had a heat-stable non-endotoxic effect on the LAL system. Average endotoxin levels in faeces of GF, SPF and CV mice were 0.2, 0.8 and 17 to 24 μg/g wet weight, respectively. Results suggest that the microbiological status of mice influences not only the faecel endotoxin level but also the specificity of the test reaction.

Scanning electron microscopic studies on some chemically modified bast fibres

The surface morphology of dewaxed jute and of dewaxed and scoured flax and ramie fibres, and the effect of chemically modified morphologies were compared using scanning electron microscopy (SEM). Limited oxidation results in the removal of surface impurities of the bast fibres, producing strands which are clearly distinguishable in the SEM. Treatment of the oxy-fibres with excess phenol (P) and formaldehyde (F) at pH 8 leads to permanentin situ deposition of P-F resin moieties, which makes the strands less clearly visible. Modification of the P-F treated oxy-fibres by vinyl grafting leads to further masking of the fibre strands due to measurable vinyl deposition; in the SEM the fibre strands appear closely cemented together by the grafted-on vinyl polymer. On exposure to a standard microbiological degradative environment, damage to the fibre strands takes place in the order jute ≫ flat ⩾ ramie; oxy-jute ≫ oxy-flax ⩾ oxy-ramie. Each fibre system suffers little microbiological degradation, thereby showing high rot resistance, when the respective oxy-fibres are modified by P-F treatment and also by vinyl grafting in a subsequent step. At this stage the difference between the three fibre systems in rot resistance becomes slight. The SEM observations are supported by analysis of tensile strength (TS) and retention of TS after exposure to a standard microbiological degradative environment.

The environmental analysis of archaeological sites

The microbiologically static environment found in stone chambers of virgin tombs is probably related to the presence of amines. In this paper analyses of the microbiological environments of the tomb of Torazuka in Japan and the tomb of Nefertari in Egypt are discussed.

Physiological relationships between microbiological status and dietary copper levels in the pig

Ten germ-free pigs and 10 conventionally reared pigs were fed one of two nutritionally balanced diets containing either 16 ppm Cu (basal) or 283 ppm Cu (high-Cu) to evaluate the physiological relationships between Cu and microbiological environment. Germ-free pigs tended to have higher ADG and average daily feed intake (ADFI) than conventionally reared pigs. Feeding the high-Cu diet tended to reduce ADG and ADFI in germ-free pigs but it increased ADG and ADFI in conventionally reared pigs. Hemoglobin and hematocrit were higher in germ-free pigs than in conventionally reared pigs (P less than .001), and hematocrit (P less than .01) and erythrocyte count (P less than .06) were reduced by feeding the high-Cu diet. Germ-free pigs had lower total leukocyte count (P less than .01) and the relative percentages of differentiated leukocytes were altered compared with conventionally reared pigs. Feeding the high-Cu diet increased the percentage of band neutrophils and monocytes in germ-free pigs but reduced the percentage of these cells in conventionally reared pigs (P less than .04). Germ-free pigs had higher concentrations of Cu and Zn in liver and plasma (P less than .001) and greater plasma ceruloplasmin oxidase activity (P less than .001) than conventionally reared pigs did. The high-Cu diet increased liver Cu and Zn (P less than .001) and plasma Cu (P less than .001) and reduced liver and plasma Fe (P less than .05). Organ weights (g/kg BW) differed between germ-free and conventionally reared pigs, and feeding the high-Cu diet reduced thymus weights (P less than .002). Intestinal weight and thickness were reduced in germ-free pigs, and feeding the high-Cu diet generally reduced villus height and width and crypt depth in germ-free pigs, whereas it increased these measurements in conventionally reared pigs.

The microbiology and chemotherapy of odontogenic infections

This article reviews the complexity of the microbiological environment of odontogenic infections. With an understanding of the organisms involved, the appropriate antibiotic can be chosen. A review of current antibiotic choices and the rationale for their selection is also presented.

Research Note: Toe Scratches Cause Scabby Hip Syndrome Lesions

Scabs and scratches in the hip region of chicken carcasses have become the single most common cause of downgrading and required trimming at processing in some areas of the United States. Repeatable correlations with microbiological agents, environment, and nutrition have not been observed. The present report provides evidence that scabs and scratches, present at processing, are the result of injuries inflicted by toenails of birds as they climb on one another. Onychectomy (removal of approximately two-thirds of the distal phalanx) of all four digits of each foot prior to chick placement resulted in 3.7 and 4.8-fold reductions in subjective lesion scores and 7 to 10-fold increases in the percentage of USDA Grade A carcasses at a commercial processing plant.

Late toxicity of total body irradiation with bone marrow transplantation in a rat model

In defined-flora, barrier-maintained rats, radiation nephritis is the principle late toxicity seen after high dose-rate total body irradiation (TBI), when hematologic toxicity is prevented by bone marrow transplantation (BMT). Pneumonitis develops only if rats are placed in a conventional microbiological environment during and after BMT. Low dose-rate TBI gives qualitatively similar late toxicity, but at radiation doses twice as large. Fractionation of the TBI has little effect on the bone marrow ablation doses, but results in increased gastrointestinal and renal tolerance. The addition of immunosuppressive or cytotoxic drugs (cyclosporine-A, methotrexate, cis-platinum) after TBI and BMT greatly decreases the dose of TBI that can be tolerated. The use of a cyclophosphamide plus cytosine arabinoside conditioning regimen prior to TBI and BMT increases the bone marrow ablation dose, but has no effect on acute gastrointestinal toxicity or on renal toxicity. These results indicate that substantial late toxicity may be associated with the TBI conditioning regimens used for BMT even in the absence of cytotoxic and antibiotic drugs, immunosuppressive agents, infection and graft-versus-host disease; and that radiation may be a contributing factor in the nephritis sometimes observed after TBI and BMT.

Optimal control of some bilinear systems with aftereffect

The optimal control of bilinear systems with aftereffect is considered. A class of systems is identified for which the optimal control is constructed by solving linear differential equations. Recursive formulas are derived for this solution. As an example, we analyse a bilinear model with aftereffect of the process of bacterial growth in a microbiological controlled environment. A system is usually called bilinear if the evolution equations are linear in the phase coordinates for fixed controls and in the controls for fixed coordinates /1, 2/. Systems of this kind are used for modelling a variety of control processes, including processes in biological systems /3–5/, etc.

A technique for predicting urea release from coated urea in wetland soil

Abstract A simple technique for measuring urea release from different coated urea fertilizer materials in simulated wetland soil has been developed and tested. The laboratory soil system used simulates physical, chemical, and microbiological environments of wetland soils under field conditions. Laboratory and field values for urea release are in good agreement.

Nosocomial infections in immunocompromised children : Hughes WT, Townsend TR: Am J Med 1981; 70: 412–416

Immunocompromised children are at high risk for developing nosocomial infections which may cause significant morbidity and mortality in this population. In paediatric oncology, reported prevalence of nosocomial infections varies from 10 to 20%. Major predisposing factors are neutropenia, central venous catheter, corticosteroid therapy and hospital construction or renovation for invasive aspergillosis. The management of patients with febrile neutropenia should take into account the previous history of infection and the microbiologic environment of each department. Nowadays, Gram positives infections are predominant, but fungal infections remain a major threat. In organ transplant recipients, wound infections are the main early problems, followed by viral infections often due to the donor CMV seropositivity. In HIV-infected children, nosocomial infections are difficult to define, and can implicate unusual pathogens. In general, adapted preventive infection control strategy warrants prospective studies.

Microbiologic Environment of the Conventional Operating Room

Areas of potential contamination of the surgical wound in the conventional operating rooms include the back table, the unsterile suction receptacle, and the lack of a positive pressure relationship between the operating room and adjacent areas. Use of an impermeable hood with a large mask diminished contamination of the instrument table and the the wound from fallout of bacteria from the surgical team. The level of airborne bacterial comtamination in the operating room can be reduced by limiting the traffic and controlling the activity and the number of operating room personnel. Higher rates of postoperatively wound sepsis were noted in older operating rooms, particularly with difficult procedures and those performed later in the day. Conventional operating rooms should be categorized by the level of room air exchange per hour and the level of airborne bacterial contamination.